I like to give ppl shit for using it, but honestly it doesn't seem very useful to me, I think addons like omnibar are way better - but I guess it's been the norm to use interruptbar for a lot of years now, so it's "ok".
One thing I don't understand, is that blizzard openly said in the past that they don't have big focus on the standard UI of the game, because addon creators can fill any gap anyone might have. Yet in "competitive" play you're not allowed to use those addons that make the standard ui less terrible, and you're stuck with the horrifying shit UI that they cba fixing.
Even more hilarious is that you need to get addons to avoid certain bugs in the standard UI, that they for some reason don't want to fix -
like players joining your group/raid while you're in combat,
or like your player/focus frame changing position after you DC even though their position is "locked" (......)
or like arena frames bugging out when you dc and rejoin an arena, oh wait can't fix that lmao nice ui
I want to add to that, I don't know if it's still there, but there used to be a bug where you needed an addon CombatLogFixer exDee